feat: Implement end-to-end automated Java test generation pipeline

[Zapper9982]

This commit introduces a comprehensive system for automated Java JUnit 5 test case generation using Large Language Models (LLMs), with a focus on iterative improvement based on JaCoCo code coverage reports.

Key Features:

• Pre-processing: I remove comments and prepare your Java code for analysis.
• Code Analysis: I identify Spring Boot controllers and services as targets for test generation.
• Langchain Integration: I chunk your source code, generate embeddings (BAAI/bge-small-en-v1.5), and store them in ChromaDB.
• LLM-Powered Test Generation: I use Google's Gemini-1.5-flash model via Langchain's RetrievalQA to generate JUnit 5 test cases. This includes a retry mechanism with feedback for failed tests.
• JaCoCo-Based Iteration:
  • I execute the generated tests using Maven or Gradle.
  • I parse JaCoCo XML reports to determine overall line coverage and method-specific coverage.
  • If coverage is below a configurable target (default 90%), I identify under-tested methods.
  • I then refine prompts to the LLM to focus on these specific methods in subsequent iterations.
  • This process repeats for a configurable maximum number of iterations.
• Configuration: Key parameters such as the Spring Boot project root, Google API key, build tool, max iterations, and target coverage are configurable via environment variables.
• Central Orchestration: src/main.py manages the entire pipeline flow.
• GitHub Actions Workflow: A CI workflow (.github/workflows/coverage_check.yml) is implemented to:
  • Run the test generation pipeline on pushes/pull_requests.
  • Fail PRs if the target code coverage is not met.
  • Requires GOOGLE_API_KEY to be set as a repository secret.
• Documentation:
  • README.md has been updated with detailed instructions on setup, configuration, and execution.
  • run.sh script provided as a helper to set environment variables and launch the pipeline.

The system is designed to significantly reduce your manual effort in writing unit tests and help maintain high code coverage standards.